/*
 * ! Ext JS Library 3.0.0 Copyright(c) 2006-2009 Ext JS, LLC licensing@extjs.com
 * http://www.extjs.com/license
 */
Ext.ns('Ext.ux.grid');

/**
 * @class Ext.ux.grid.BufferView
 * @extends Ext.grid.GridView A custom GridView which renders rows on an
 *          as-needed basis.
 */
Ext.ux.grid.BufferView = Ext.extend(Ext.grid.GridView, {
	/**
	 * @cfg {Number} rowHeight The height of a row in the grid.
	 */
	rowHeight : 19,

	/**
	 * @cfg {Number} borderHeight The combined height of border-top and
	 *      border-bottom of a row.
	 */
	borderHeight : 2,

	/**
	 * @cfg {Boolean/Number} scrollDelay The number of milliseconds before
	 *      rendering rows out of the visible viewing area. Defaults to 100.
	 *      Rows will render immediately with a config of false.
	 */
	scrollDelay : 100,

	/**
	 * @cfg {Number} cacheSize The number of rows to look forward and backwards
	 *      from the currently viewable area. The cache applies only to rows
	 *      that have been rendered already.
	 */
	cacheSize : 20,

	/**
	 * @cfg {Number} cleanDelay The number of milliseconds to buffer cleaning of
	 *      extra rows not in the cache.
	 */
	cleanDelay : 500,

	initTemplates : function() {
		Ext.ux.grid.BufferView.superclass.initTemplates.call(this);
		var ts = this.templates;
		// empty div to act as a place holder for a row
		ts.rowHolder = new Ext.Template('<div class="x-grid3-row {alt}" style="{tstyle}"></div>');
		ts.rowHolder.disableFormats = true;
		ts.rowHolder.compile();

		ts.rowBody = new Ext.Template(
				'<table class="x-grid3-row-table" border="0" cellspacing="0" cellpadding="0" style="{tstyle}">',
				'<tbody><tr>{cells}</tr>',
				(this.enableRowBody
						? '<tr class="x-grid3-row-body-tr" style="{bodyStyle}"><td colspan="{cols}" class="x-grid3-body-cell" tabIndex="0" hidefocus="on"><div class="x-grid3-row-body">{body}</div></td></tr>'
						: ''), '</tbody></table>');
		ts.rowBody.disableFormats = true;
		ts.rowBody.compile();
	},

	getStyleRowHeight : function() {
		return Ext.isBorderBox
				? (this.rowHeight + this.borderHeight)
				: this.rowHeight;
	},

	getCalculatedRowHeight : function() {
		return this.rowHeight + this.borderHeight;
	},

	getVisibleRowCount : function() {
		var rh = this.getCalculatedRowHeight();
		var visibleHeight = this.scroller.dom.clientHeight;
		return (visibleHeight < 1) ? 0 : Math.ceil(visibleHeight / rh);
	},

	getVisibleRows : function() {
		var count = this.getVisibleRowCount();
		var sc = this.scroller.dom.scrollTop;
		var start = (sc == 0 ? 0 : Math.floor(sc
				/ this.getCalculatedRowHeight())
				- 1);
		return {
			first : Math.max(start, 0),
			last : Math.min(start + count + 2, this.ds.getCount() - 1)
		};
	},

	doRender : function(cs, rs, ds, startRow, colCount, stripe, onlyBody) {
		var ts = this.templates, ct = ts.cell, rt = ts.row, rb = ts.rowBody, last = colCount
				- 1;
		var rh = this.getStyleRowHeight();
		var vr = this.getVisibleRows();
		var tstyle = 'width:' + this.getTotalWidth() + ';height:' + rh + 'px;';
		// buffers
		var buf = [], cb, c, p = {}, rp = {
			tstyle : tstyle
		}, r;
		for (var j = 0, len = rs.length; j < len; j++) {
			r = rs[j];
			cb = [];
			var rowIndex = (j + startRow);
			var visible = rowIndex >= vr.first && rowIndex <= vr.last;
			if (visible) {
				for (var i = 0; i < colCount; i++) {
					c = cs[i];
					p.id = c.id;
					p.css = i == 0 ? 'x-grid3-cell-first ' : (i == last
							? 'x-grid3-cell-last '
							: '');
					p.attr = p.cellAttr = "";
					p.value = c.renderer(r.data[c.name], p, r, rowIndex, i, ds);
					p.style = c.style;
					if (p.value == undefined || p.value === "") {
						p.value = "&#160;";
					}
					if (r.dirty && typeof r.modified[c.name] !== 'undefined') {
						p.css += ' x-grid3-dirty-cell';
					}
					cb[cb.length] = ct.apply(p);
				}
			}
			var alt = [];
			if (stripe && ((rowIndex + 1) % 2 == 0)) {
				alt[0] = "x-grid3-row-alt";
			}
			if (r.dirty) {
				alt[1] = " x-grid3-dirty-row";
			}
			rp.cols = colCount;
			if (this.getRowClass) {
				alt[2] = this.getRowClass(r, rowIndex, rp, ds);
			}
			rp.alt = alt.join(" ");
			rp.cells = cb.join("");
			buf[buf.length] = !visible ? ts.rowHolder.apply(rp) : (onlyBody
					? rb.apply(rp)
					: rt.apply(rp));
		}
		return buf.join("");
	},

	isRowRendered : function(index) {
		var row = this.getRow(index);
		return row && row.childNodes.length > 0;
	},

	syncScroll : function() {
		Ext.ux.grid.BufferView.superclass.syncScroll.apply(this, arguments);
		this.update();
	},

	// a (optionally) buffered method to update contents of gridview
	update : function() {
		if (this.scrollDelay) {
			if (!this.renderTask) {
				this.renderTask = new Ext.util.DelayedTask(this.doUpdate, this);
			}
			this.renderTask.delay(this.scrollDelay);
		} else {
			this.doUpdate();
		}
	},

	doUpdate : function() {
		if (this.getVisibleRowCount() > 0) {
			var g = this.grid, cm = g.colModel, ds = g.store;
			var cs = this.getColumnData();

			var vr = this.getVisibleRows();
			for (var i = vr.first; i <= vr.last; i++) {
				// if row is NOT rendered and is visible, render it
				if (!this.isRowRendered(i)) {
					var html = this.doRender(cs, [ds.getAt(i)], ds, i, cm
									.getColumnCount(), g.stripeRows, true);
					this.getRow(i).innerHTML = html;
				}
			}
			this.clean();
		}
	},

	// a buffered method to clean rows
	clean : function() {
		if (!this.cleanTask) {
			this.cleanTask = new Ext.util.DelayedTask(this.doClean, this);
		}
		this.cleanTask.delay(this.cleanDelay);
	},

	doClean : function() {
		if (this.getVisibleRowCount() > 0) {
			var vr = this.getVisibleRows();
			vr.first -= this.cacheSize;
			vr.last += this.cacheSize;

			var i = 0, rows = this.getRows();
			// if first is less than 0, all rows have been rendered
			// so lets clean the end...
			if (vr.first <= 0) {
				i = vr.last + 1;
			}
			for (var len = this.ds.getCount(); i < len; i++) {
				// if current row is outside of first and last and
				// has content, update the innerHTML to nothing
				if ((i < vr.first || i > vr.last) && rows[i].innerHTML) {
					rows[i].innerHTML = '';
				}
			}
		}
	},

	layout : function() {
		Ext.ux.grid.BufferView.superclass.layout.call(this);
		this.update();
	}
});
